1. Field of the Invention
The invention relates to a device for removing a wetting liquid from one or more capillaries. The purpose of the invention is to simplify the removal of a liquid from capillaries or to enable the liquid to be obtained as a free-flowing liquid.
2. Description of Related Art
Capillaries are narrow spatial structures in which surface effects of liquids occur. They can have any cross-sectional shape, including tubes and gaps. The dimensions of the cross section are in the millimeter to sub-micron region in at least one direction. The capillaries can have any desired spatial course.
Capillaries can exist as discrete structures in the form of individual straight or bent tubes having a relatively thin wall, or they can be in the form of a tube passing through a body. Furthermore, they can be pores in an open-pore porous body or sintered body or in the form of spaces between closely packed fibers in the form of paper, nonwovens or felt. They can furthermore have the shape of narrow gaps.
The surface of a wetting liquid adjoining a solid wall forms a contact angle from zero degrees to less than ninety degrees with the wall. In other words, wetting liquids have a contact angle which is greater than zero. Owing to their surface tension, wetting liquids are drawn into capillaries until the latter are completely filled. If a small force acts on the liquid at the exit end of the capillaries, the surface tension can hold the liquid in the capillaries and prevent it from exiting. The liquid can be forced to exit from the end of the capillaries by a sufficiently large pressure difference in the liquid between the capillary entrance and the capillary exit.
European Patent No. 336,483 discloses a device for separating an initially introduced liquid. The device consists of a first open-pore membrane (separator membrane) and a second open-pore membrane (collector membrane). The collector membrane is directly adjacent to the side of the separator membrane. The part of the liquid introduced on the one side of the separator membrane and which has passed through the separator membrane enters the collector membrane where it remains. The liquid collected in the collector membrane below the separator membrane can be reacted with a reagent applied to the collector membrane or the collected liquid can be washed out of the collector membrane by a further liquid and subsequently analyzed. The liquid separated therefrom by the separator membrane and collected in the collector membrane can thus remain in the collector membrane during its further analysis or it can be washed out, in which case it is mixed with a further liquid. In either case, there is not obtained a free-flowing liquid that consists of only the part of the initially introduced liquid which has been separated therefrom by the separator membrane.
For the analysis or use of liquids which have been collected with the aid of capillaries or separated from a liquid medium, it may be advantageous or necessary to obtain the liquid from the capillaries as a free-flowing liquid which is not mixed with any further liquid.